JPH0359262B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an injection amount control device in a fuel injection device for an internal combustion engine.

The amount of injection in conventional distribution fuel injection pumps is controlled by moving the ring-shaped member that opens and closes the overflow port in the axial direction of the plunger using a mechanical governor, and changing the effective pumping stroke of the plunger. is being done. However, when trying to electronically control the injection amount, following the above configuration as is would require a high-grade actuator, position sensor, etc. to precisely control the position of this ring member, making it complicated and expensive. I have no choice but to do so.

In order to avoid such problems, a method was developed that uses a solenoid valve instead of a ring-shaped member or a precision actuator to control the injection amount, as disclosed in Japanese Patent Laid-Open No. 56-151228.
It is known from the publication no.

In such a system, the fuel injection amount is determined by the closing period of the solenoid valve. However, the method in the above publication calculates the closing period of the solenoid valve based on the signal from the nozzle lift sensor.
There is also the problem that a nozzle lift sensor that is expensive and has a complicated structure is required. Additionally, if fuel is cut off during deceleration, for example, a signal from the nozzle lift sensor cannot be obtained, making it impossible to determine the timing to open the solenoid valve when restarting injection, making accurate injection amount control difficult. Ta.

In addition, there is also known a device for controlling the injection amount using a solenoid valve, as disclosed in Japanese Patent Application Laid-open No. 56-154134.

This device outputs an injection start timing signal according to the operating status, closes the solenoid valve based on this injection start timing signal, calculates the closing period of the solenoid valve based on this injection start timing signal, and opens the solenoid valve. The injection end timing signal is obtained for this purpose. In this system, if the injection start timing signal is output even when fuel injection is restarted after a fuel cut, it is possible to determine the end of injection, that is, the timing to open the solenoid valve, but there are other problems.

In other words, in such a type of fuel injection pump that injects fuel according to the reciprocating motion of a plunger whose phase changes according to the rotation of a cam, the phase of the plunger is usually controlled by a so-called timer mechanism (in particular, (It is also shown in both JP-A-56-151228 and JP-A-56-154134). However, in JP-A-56-154134, both the injection start timing signal and the injection end timing signal are determined by the crank angle on the engine side, which has no relation to the phase of the plunger. If the position moves extremely to the retarded side, the injection start timing signal will be output before the plunger starts pumping, and the solenoid valve will be closed.In such a case, the injection start timing signal will be used as the starting point. The calculated injection end timing signal would be output at a timing earlier than when the actually required injection amount is reached, making it impossible to accurately control the injection amount.

In other words, in JP-A-56-154134, since the opening timing of the solenoid valve is determined by the rotation angle of the engine crankshaft, if the phase of the plunger changes significantly, the injection Volume control was becoming inaccurate.

In view of the above problems, the present invention provides a plunger phase sensor that detects the phase of the plunger, and determines the opening timing of the solenoid valve based on the plunger phase signal, thereby achieving accurate injection amount control at all times and at low cost. The purpose is to provide a simple device.

The present invention will be explained below with reference to embodiments shown in the figures.

FIG. 1 shows a configuration including a partial cross section of an injection pump when the present invention is applied to a known face cam type distribution injection pump 1 for diesel engines. This pump 1 uses a plunger 2 which is rotated and reciprocated by a face cam 3 to pressurize fuel sucked in from an intake port 16 in a pump chamber 5 serving as a pressurizing chamber, and then a suction valve 4 is released from a distribution port 6 at the foot of each cylinder. It is of a type that is fed under pressure to a nozzle (not shown). In the present invention, in addition to the above configuration, the pump chamber 5
A solenoid valve 8 having a spool-shaped valve body 8a is disposed at one end of the overflow port (overflow passage) 7, which is constantly in communication with the pressure of is arranged to overflow into the low pressure housing. The opening and closing operations of the solenoid valve 8 are controlled by a computer 9 as a control circuit.

On the other hand, the computer 9 has a known rotation sensor 10, which is a combination of tooth-like protrusions carved at regular crank angles on the flywheel of an engine (not shown) and an electromagnetic pickup, which responds to the driver's accelerator pedal depression. A potentiometer-type load sensor 11 that generates an output (if necessary, it is also possible to use an idle switch 12 that detects the idle state with the accelerator pedal) is connected, and a pump cam shaft (coaxial with the plunger 2) is connected. A bottom dead center sensor 13 (not necessarily limited to the bottom dead center of a fuel injection cylinder) as a plunger phase sensor consisting of a combination of a protrusion and an electromagnetic pickup provided at a position corresponding to the bottom dead center of each cylinder Any sensor that can detect the reference angle with respect to the stroke of the plunger 2) and the known temperature sensor 14 and pressure sensor 15 that detect cooling water temperature, intake temperature, atmospheric pressure, intake pressure, etc.
etc., and the computer 9 is configured to be able to detect the operating state of the engine and the environmental state at any time.

Next, the detailed configuration inside the computer 9 will be explained with reference to FIG. The part surrounded by a dashed line in FIG. 2 is a computer, and in this embodiment, a case of digital control using a microcomputer will be described. The configuration is centered around a central processing unit (CPU) 101, a timer unit 102 that generates time signals used for calculations and control, an interrupt control section 103 that starts predetermined interrupt processing based on information given from the outside, and a lower section. Point sensor 13
and a digital input port 104 for inputting digital signals from the idle switch 12 and the rotation sensor 1.
Analog information from a rotation counter unit 105, which is a type of frequency-voltage (F-V) converter that extracts rotation information based on input from 0, a load sensor 11, a pressure sensor 14, a temperature sensor 15, etc. Analog input port 109, memory 10 that stores various characteristic data necessary for control in advance
7, and an output circuit section that controls the opening and closing of the solenoid valve 8 as an actuator, and these 101 to 101
Each of the units 108 is connected by a bus line 104 for mutually exchanging input/output signals.

Next, the operation of this embodiment will be explained using the flowchart shown in FIG. When the plunger 2 (integrated with the camshaft) of the injection pump 1 rotates and reaches the bottom dead center of a certain cylinder, a bottom dead center signal is sent from the bottom dead center sensor 13 to the computer 9. computer 9
When this bottom dead center signal is input to the digital input port 104 (step 201), the interrupt control section 103 is activated and the interrupt processing shown in FIG. 3 is started within the CPU 101. (Step 202). Simultaneously with the start of the interrupt, the CPU 101 starts counting time in step 203 using the timer 102, and instructs the output circuit 10 to close the solenoid valve 8 in step 204.
Command to 8.

This interrupt processing flows through steps 202 to 213, and in steps 205, 206, and 207, information on the rotation speed, load, temperature, and pressure is taken in, and in step 208, the solenoid valve closing time data stored in the memory 107 in advance is input. T ₁ is determined by, for example, a two-dimensional map search based on the rotational speed and load. (The longer T ₁ is, the longer the overflow caused by the solenoid valve 8 is, the longer the effective pumping time of the injection pump 1 is, and the more the injection amount increases. In other words, the memory 107 stores the T for the optimum injection amount according to the load and rotation speed. ₁ is memorized). Then, in step 209, the valve closing time _T1 is corrected according to the temperature (e.g., engine cooling water temperature, intake air temperature) and pressure (e.g., atmospheric pressure, intake pressure, etc.), and in step 210, the solenoid valve is closed after this correction. Valve time data T ₁ ′ is CPU
is set in the output comparison register in This output comparison register activates the output circuit when the elapsed time from the reference time matches a preset time, and in the case of the present invention, it starts counting from the start of the interrupt (i.e., the bottom dead center of the pump 1). When the time T ₁ ' set in step 211 is reached, the output circuit 108 is commanded to open the solenoid valve 8 in step 212.

During the above process, in the injection pump 1, the plunger 2 starts to pump the fuel (inhaled in advance from the suction port 16) in the pump chamber 5 according to the lift of the cam 3 due to the rotation of the plunger, and the fuel is pumped. Fuel is sent from the distribution port 6 through the suction valve 4 to the nozzles provided in each cylinder of the engine, and fuel is injected when the fuel pressure reaches the nozzle opening pressure or higher. Then, when the time T ₁ ' calculated by the computer 9 has elapsed from the bottom dead center, the solenoid valve 8 opens as described above, and the high-pressure fuel in the pump chamber 5 overflows into the low-pressure housing via the overflow port 7. , the fuel pressure drops rapidly and fuel injection ends. That is, by arbitrarily changing the time T ₁ ' until the solenoid valve 8 opens, the injection amount of the pump 1 can be arbitrarily controlled. In other words, if the solenoid valve 8 is configured to close at the bottom dead center of the plunger 2 as in this embodiment, the closing period of the solenoid valve 8 always corresponds to the fuel injection amount, and in effect The injection amount is controlled only by the opening timing of the solenoid valve 8.

In the above example, the closing time of the solenoid valve was handled directly as "time", but it can be handled in the same way by handling it as "angle" information of crank angle or cam angle in the computer and performing "angle → time conversion". control is realized.

As described above, the present invention is provided with a plunger phase sensor that detects the phase of the plunger, and calculates the opening timing of the solenoid valve using the signal from the plunger phase sensor as a reference signal, so the system is inexpensive and simple. In addition, a reference signal is obtained that determines the opening timing of the solenoid valve regardless of whether fuel is being cut or not, and furthermore, the opening timing of the solenoid valve automatically changes according to the phase change of the plunger. This has the excellent effect of always being able to accurately determine the injection amount.

[Brief explanation of drawings]

FIG. 1 is an overall configuration diagram showing an embodiment of the present invention;
Figure 2 is a detailed configuration diagram of the control circuit in Figure 1;
The figure is a flowchart showing the arithmetic processing procedure in the control circuit. 1...Fuel injection pump, 2...Plunger, 5
... Pump chamber forming a fuel pressurizing chamber, 7 ... Overflow passage, 8 ... Solenoid valve, 9 ... Computer forming a control circuit, 10 ... Rotation sensor, 11 ... Load sensor, 13 ... Bottom dead point sensor, 14... pressure sensor, 15... temperature sensor, 101... central processing unit.

Claims (1)

[Claims] 1. An overflow passage whose one end always communicates with the fuel pressurizing chamber of the fuel injection pump that pumps fuel during the internal combustion period according to the reciprocating motion of the plunger whose phase changes according to the rotation of the cam, and whose other end communicates with the low pressure side; The electromagnetic valve is disposed in the middle of this overflow passage, and has an electromagnetic valve that opens and closes the overflow passage, and an operating condition detector that detects various operating conditions of the engine. In a fuel injection amount control device that determines a fuel injection amount by controlling at least the opening timing of a valve, a plunger is provided on the plunger to detect a predetermined phase of the plunger and generates a phase signal of the plunger. a phase sensor;
A fuel injection control device comprising: calculation means for inputting a signal from the plunger phase sensor and calculating the opening timing of the electromagnetic valve based on the plunger phase signal.